Japanese Patent Application Publication No. 2009-175614 discloses a wavelength selective switch that separates signal light including a plurality of signal components having different wavelengths into respective signal components so that the separated signal components are output from different output ports. The wavelength selective switch comprises a microelectromechanical system (MEMS) mirror that switches the reflection directions of the respective signal components and a controller that applies a driving voltage to the MEMS mirror. The controller includes a firmware storage unit that stores a predetermined program, a central processing unit (CPU) that operates by loading the program from the firmware storage unit, and a digital-to-analog converter that receives a control signal from the CPU to generate the driving voltage.
Japanese Patent Application Publication No. 2012-105222 discloses an optical channel monitor as an optical transmission device that is used in an optical communication field. This optical channel monitor comprises an optical fiber that transmits an optical signal obtained by multiplexing a plurality of optical signals having different wavelengths, a coupler that allows a portion of the optical signal to branch off from the optical fiber, and a dispersive device and a light-receiving element that disperse the branched optical signal to detect the intensity of each wavelength. Moreover, this optical channel monitor comprises a random access memory (RAM) in which the central wavelength of each channel calculated from the detection results in the light-receiving element is temporarily stored and a nonvolatile memory such as a flash memory in which the central wavelength of each channel is periodically stored in order to compute a variation over time in the central wavelength of each channel.